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SELECTED RADIOISOTOPES IN ANIMAL TISSUES IN NEVADA: 90SR AND 137CS MEASUREMENTS FROM 1956 TO 1977
Citation:
Smith, D. AND V. Andrews. SELECTED RADIOISOTOPES IN ANIMAL TISSUES IN NEVADA: 90SR AND 137CS MEASUREMENTS FROM 1956 TO 1977. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-81/045.
Description:
Measurements have been made since 1956 of the strontium-90 and cesium-137 concentrations in tissues from cattle, deer, and bighorn sheep living on and around the Nevada Test Site (NTS). Examination of this data cumulation indicates that the measured tissue concentrations reflect global fallout rather than local sources of these isotopes. Maximum strontium-90 concentrations in bone are related to exposure during maximum bone growth. During, or immediately following, periods of high fallout, younger animals exhibited higher concentrations of strontium-90 in bone. During low-fallout periods older animals, which had been young during heavy fallout periods, had the highest concentrations of strontium-90 in bone. The effective half-life of strontium-90 in bone of desert bighorn sheep is estimated to be 4.8 years while the effective half-life of cesium-137 in soft tissue appears to be only a few weeks. The maximum observed concentration of cesium-137 in edible tissue was 2,900 picocuries per kilogram in liver from a deer collected 5 weeks after a nearby nuclear cratering experiment. Using standard-man data, the daily consumption of 500 grams of such tissue would result in an annual dose of 32 millirem, which is 6.4 percent of the radiation protection guide established for individuals of the general population. The husbandry, necropsy, and histopathological records of the NTS beef herd indicate that the nuclear testing program has had no observable long-term impact on the herd.